This invention relates generally to antennas and more particularly to a multiband, multimode antenna which provides both a communication antenna section and a directional antenna section.
In the past it has been conventional practice to provide separate antennae for such purposes. Thus, there may be as many as three different communication antennas and two directional antenna portions to provide the capability of the antenna of the present invention. This antenna is specifically designed for use with aircraft; that is, with fixed-wing airplane and helicopter-type devices.
In this case, it is highly desirable that the over-all vertical height of the antenna be as small as possible. Antennas of this type are generally known; for example, Adcock Arrays. Such antennas may extend over a large area, which, however, is not available on aircraft.
Furthermore, it is known to increase the bandwidth of such an antenna by capacitive top-loading. Such a device will form a monopole antenna which is electrically short; that is, less than one-fourth wavelength. However, in the past, the use of capacitive top-loading has not been used for aircraft antennas because of the bulk required for top-loading.
It is, accordingly, an object of the present invention to provide a top-loaded monopole antenna suitable for use with aircraft.
Another object of the invention is to provide a single antenna structure capable of receiving and transmitting for communication purposes, three frequency bands in the megahertz region.
A further object of the present invention is to provide such an antenna which cooperates with two wires for providing a directional antenna system which may be used for homing purposes.